Cross-linking of porous gel-spun ultra-high molecular weight polyethylene by means of electron beam irradiation

Summary Porous gel-spun ultra-high molecular weight polyethylene (UHMWPE) fibres, consisting of large folded chain lamellae linked to each other by means of tie molecules, have been Irradiated at room temperature by means of high energy electrons.From a discrepancy in yield of cross-links per unit of absorbed irradiation energy as calculated from sol-gel measurements and equilibrium swelling experiments, it was concluded that the tie molecules are preferentially scissioned, and thereby separating the different lamellae. At high irradiation doses the lamellae are linked again by cross-links between consecutive lamellae.     

On the theoretical strength of gelspun/hotdrawn ultra-high molecular weight polyethylene fibres

Summary The fraction of load carrying chains in various gelspun/hotdrawn ultra high molecular weight polyethylene (UHMWPE) fibres was evaluated on the basis of a recent morphological model. A linear relation was found between the strength of the fibre and the fraction of load carrying chains, calculated by this method. By extrapolation of this relation to a fraction of load carrying chains of unity, a theoretical strength of 30±3 GPa was estimated for polyethylene.     

Creep resistance and high temperature strength of poly(p-xylylene) fibers

Summary High-strength and high-modulus poly(p-xylylene) (PPX) fibers show no creep at room temperature and retain at 200°C, in air or in nitrogen atmosphere, still 50 to 60% of their tensile strengths at room temperature, whereas the modulus does not change. In stress relaxation experiments PPX fibers have relaxed after 17.4 hours less than 4% of the initial stress whereas during the same period of time polyethylene fibers relax over 75% of the initial stress.     

Simple method for estimating usable bend radii for deeply etched optical rib waveguides

An easy to use and extremely fast computational technique is presented for estimating the minimum usable radius of deeply etched, curved rib waveguides. This method is based on the effective index method and estimates the radius of curvature at which the bend becomes cut off due to substrate leakage.<>     

Integrated-optic versus microoptic devices for fiber-optictelecommunication systems: a comparison

We assess the relative merits and prospects of integrated-optics in comparison with microoptic and fiber-based techniques. Firstly, the market for fiber-optic components for telecommunications is analyzed. Secondly, the technological issues which make integrated optics quite different from integrated electronics will be discussed. Thirdly, a specific comparison between the potential of the competing optical technologies will be made for the polarization-diversity hybrid and the optical wavelength (de)multiplexer, two optical devices used in networks that are based on optical frequency division multiplexing (OFDM)     

Effect of chlorosulfonation of ultra-high strength polyethylene fibres on mechanical properties and bonding with gypsum plaster

Summary Ultra-high strength polyethylene fibres were chlorosulfonated according to Kanig's technique. It has been found that the tensile strength of the fibre decreases during chlorosulfonation, whereas the Young's modulus can be increased by more than fifty percent of its original value. The interfacial bond-strength between polyethylene and gypsum plaster could be improved at least 4.8 times, amounting values of 6.3 MPa, making these fibres very suitable for use as a reinforcing material in gypsum plaster. SEM indicated that this improvement could be described to surface roughening of the fibre, due to chemical degradative stress-cracking during constrained chlorosulfonation.     

Shish kebab formation on polyethylene monofilaments

A study has been made on skin formation of melt spun polyethylene monfilaments, which were solidified in air or in cold solvents and non-solvents. Application of air or non-solvents, such as water and acetone, as cooling media induced spherulitic crystallisation of the polymer, as was revealed in the scanning electron microscope. When the flowing polyethylene melt was quenched in good solvents, a 0.5 mm thick layer of lamellar or shish kebab structures developed on the polymeric fibres. It was established that shish kebabs were formed when the solvents, in which the polymer filament was quenched, were boiling during this solidification process.     

Effects of additives on gel-spinning of ultra-high molecular weight polyethylene

Conclusions As judged from the fibre tensile strength-extrudate draw speed relationship for UHMWPE solutions in paraffin oil, carbon black particles diminish flow instabilities and extrudate irregularities as does EPDM rubber. Reductions in fibre tensile strength by both additives is caused by their weakening the fibre structure.Increasing the shear rate at the wall by using a more abrupt die geometry lowers drastically the mechanical properties of the fibres.     

Pathways Related to NLRP3 Inflammasome Activation Induced by Gold Nanorods

The widespread and increasing use of engineered nanomaterials (ENM) increases the risk of human exposure, generating concern that ENM may provoke adverse health effects. In this respect, their physicochemical characteristics are critical. The immune system may respond to ENM through inflammatory reactions. The NLRP3 inflammasome responds to a wide range of ENM, and its activation is associated with various inflammatory diseases. Recently, anisotropic ENM have become of increasing interest, but knowledge of their effects on the immune system is still limited. The objective of the study was to compare the effects of gold ENM of different shapes on NLRP3 inflammasome activation and related signalling pathways. Differentiated THP-1 cells (wildtype, ASC- or NLRP3-deficient), were exposed to PEGylated gold nanorods, nanostars, and nanospheres, and, thus, also different surface chemistries, to assess NLRP3 inflammasome activation. Next, the exposed cells were subjected to gene expression analysis. Nanorods, but not nanostars or nanospheres, showed NLRP3 inflammasome activation. ASC- or NLRP3-deficient cells did not show this effect. Gene Set Enrichment Analysis revealed that gold nanorod-induced NLRP3 inflammasome activation was accompanied by downregulated sterol/cholesterol biosynthesis, oxidative phosphorylation, and purinergic receptor signalling. At the level of individual genes, downregulation of Paraoxonase-2, a protein that controls oxidative stress, was most notable. In conclusion, the shape and surface chemistry of gold nanoparticles determine NLRP3 inflammasome activation. Future studies should include particle uptake and intracellular localization.